What is West Nile virus?

As cases of West Nile virus emerge around the country, here’s what you should know
August 22, 2019

Summer comes to an official close next month, but a hallmark summer pest will remain active in some parts of Texas through Halloween—which is fitting because they want to suck your blood. Mosquito bites are certainly unpleasant, but every now and then, they can go from bothersome to life-threatening if they transfer West Nile virus (WNV).

The first case of West Nile virus this year in Texas was recently confirmed in El Paso County, so we spoke with an infectious disease expert, Cristie Columbus, MD, associate dean for the Texas A&M College of Medicine, to learn more about the disease.

What is the West Nile virus?

The West Nile virus is a mosquito-borne virus that can cause encephalitis (inflammation of the brain) and meningitis (inflammation of the lining of the brain and spinal cord) and can even be fatal in severe cases.

The virus has been detected in 36 states this year, and cases have occurred every summer since 1999, when it first made an appearance in the United States.

How is it contracted?

Because most people are infected through mosquito bites, the virus is most prevalent during the summer months (from June to September), when mosquitoes are more likely to breed. Mosquitoes contract the disease by feeding on infected birds.

WNV is not contagious through normal person-to-person contact. In rare cases, the virus can be transmitted via blood transfusion, organ transplant or from mother to baby during pregnancy, delivery and breastfeeding.

The people most at risk for contracting the virus are those who work outdoors or participate in outdoor activities. However, anyone living in an area where WNV is present in mosquitoes is at risk.

What are the symptoms of WNV?

According to the Centers for Disease Control and Prevention (CDC), 70 to 80 percent of people infected with WNV show no symptoms at all. The remaining 20 percent may develop symptoms two days to two weeks after being bitten by an infected mosquito. Symptomatic patients are most likely to develop a flu-like illness with fever. In addition to fever, symptoms may include:

  • Headache
  • Body aches and joint pains
  • Nausea or vomiting
  • Diarrhea
  • Rash

Most people who develop these symptoms make a complete recovery, but weakness and fatigue can last for weeks or months after infection.

In rare but extreme cases (less than 1 percent of the time), people develop a serious neurological illness such as encephalitis or meningitis. These illnesses can cause symptoms such as:

  • Headache
  • High fever
  • Neck stiffness
  • Disorientation
  • Coma
  • Tremors
  • Seizures
  • Paralysis

These neurological effects may take several weeks or months to recover from and, in some cases, can be permanent. Approximately 10 percent of people who develop a neurological illness from WNV will die.

Can it be treated?

Unfortunately, there are no vaccines or medications to treat WNV. For people who develop symptoms, over-the-counter pain relievers and fever reducers can be used to relieve some symptoms. People with mild symptoms usually recover on their own, but symptoms may last for several weeks after onset. In more severe cases, patients may need to be hospitalized to receive supportive treatment for neurological symptoms.

If you suspect that you or a family member has the virus, consult a health care provider to undergo an exam and further testing. Tests using blood samples or spinal fluid may be used to detect antibodies the immune system creates to fight infection that is present in the body. Other types of tests are available through state public health laboratories or the CDC.

Are there any actions you can take to prevent the disease?

Since there is currently no vaccine, the best method of protection is to prevent mosquito bites. People can do this by applying insect repellant whenever they go outdoors. Repellants using DEET, picaridin, IR3535 and some oil of lemon eucalyptus and para-menthane-diol products typically provide longer-lasting protection.

In addition to repellant, wear long sleeves and pants, especially during dawn and dusk, when mosquitoes are most active. Installing or repairing window and door screens can help limit the number of mosquitoes that enter indoors, as can using air conditioning when you can. Reduce the number of mosquitoes around your house by draining any nearby standing water. Empty out water-filled containers such as flowerpots, gutters, buckets, pool covers, pet water dishes and birdbaths to help limit the number of mosquitoes that breed nearby.

For more information, the CDC has many resources about protecting yourself against the West Nile virus.

— Lindsey Hendrix

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